The Main Difference between Relay and Circuit Breaker

The main difference between Relay and Circuit breaker is, the relay is a switching cum controlling device whereas the circuit breaker is a switching cum protective device. Relay and circuit breaker both are very well-known terms in electrical and electronics engineering and most of the people think that both of these work the same but there is a huge difference. Relay and Circuit Breaker can be differentiated from a circuit in various important factors. In this article, we are going to discuss about it.

What is a Relay?

The relay is a switching device that switches or routes the electrical signal or current. Basically, a relay has an electromagnetic coil and contacts. For example, an SPDT(Single Pole Double Throw) relay has a common terminal and one normally open(NO) terminal and one normally closed(NC) terminal. In normal conditions, when the relay coil is not energized the NO contact remains NO and the NC terminal remains NC. But when the relay coil is energized the NO contact becomes NC and the NC contact becomes NO. 

So a relay can perform switching, routing, and controlling functions. Relay can be also a sensing device. It can sense the Undervoltage fault(Undervoltage relay), earth leakage fault(earth leakage relay), overcurrent fault, and so many other faults. Even in most of the cases, a relay is used with circuit breakers. When the relay senses a fault it sends signals to the circuit breaker and the circuit breaker will break the circuit.

What is Circuit Breaker?

The circuit breaker is mainly an electrical protective device but it also is used as a switching device. It can break a circuit manually or automatically and closed a circuit manually. In normal conditions, the circuit breaker keeps remain the circuit in closed condition but when any fault occurs it automatically disconnects or breaks the circuit. 

There are different types of circuit breakers are available for different protection purposes. For example, an MCB or Miniature Circuit Breaker is used for the short circuit fault and overload fault. On the other hand, an RCCB or Residual Current Circuit Breaker is used to protect the leakage fault. Sometimes the circuit breaker uses a relay to sense the fault. The circuit breaker contacts and Relay both are inbuilt in a circuit breaker. The relay senses the fault and the contact mechanism breaks or makes the circuit.

Key Differences Between Relay and Circuit Breaker

1. A relay is mainly a switching device that switches or routes the current or signal whereas the circuit breaker is mainly a protective device that breaks the circuit when an electrical fault occurs.

2. Relay can control a high voltage-high current circuit with the help of a low voltage-low current circuit. On the other hand, the function of the circuit breaker is completely different.

3. You will see the uses of the relay in electronic circuits whereas you will see the uses of the circuit breaker in electrical circuits.

4. A relay can be called as a controlling device also as it controls circuits whereas the circuit breaker can be called as a switching device also as it can be used as the main switch in a circuit.

5. Relay is used in controlling circuits whereas the circuit breaker is used in protective circuits.

Read Also: 

• What is Thermal Fuse and Thermal Switch? Difference
• What is Breaker Switch? Uses, Applications
• What is RCBO? Full Form, Function, Application, Use
• What is Ground Fault Circuit Interrupter(GFCI)? Use
• Difference between Earth Fault Relay and Earth Leakage Relay

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